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Ref. No. [UMCES] CBL 2016-014
ACT VS16-05
28
RESULTS of MOORED FIELD TESTS
Moored field tests were conducted to examine the performance of the Hach LDO sensor
within both HL4 and DS5X sondes to consistently track natural changes in dissolved oxygen over
extended deployment durations of 11-18 weeks. In addition, field tests examined the reliability of
the instruments, i.e., the ability to maintain integrity or stability of data collection over time.
Reliability was determined by quantifying the percent of expected data that was recovered and
useable. The performances of the HL4 only was examined for the under ice field deployment test
in Houghton, MI and the Great Lakes profiling test in Muskegon, MI. For the Chesapeake Bay,
MD and the Kaneohe Bay, HI field deployments both instruments were included in the testing.
However, only the DS5X was equipped with an anti-fouling wiping system. The range and mean
for temperature and salinity for each test site is presented in Table 5. The final reference
temperature data was computed from the mean of two RBR thermistors and a SeaBird SBE that
were mounted at the same sampling depth as the test instrument. Immediately before each
deployment the HL4 and DS5X were exposed to a laboratory reference tank for 3-4 measurements
to confirm good working status and provide an initial offset against its latest calibration (Table 6).
In all cases the both instruments were calibrated by ACT personnel according to manufacturer
instructions just prior to the pre-deployment check.
Table 5
. Range and average for temperature, and salinity at each of the test sites during the sensor field
deployments. Temperature and salinity were measured by at least 2 RBR temperature loggers and a
SeaBird SBE 26 (or SBE26plus) mounted on the instrument rack for the duration of the deployment.
SITE
(deployment period/duration)
Temperature
°
C )
Salinity
Keweenaw Waterway
Min.
0.04
0.00
9Jan – 22Apr
Max.
5.2
0.01
(n = 104 days)
Mean
0.7
0.01
Chesapeake Bay
Min.
19.3
4.7
20May – 5Aug
Max.
36.7
13.7
(n = 78 days)
Mean
25.6
10.9
Kaneohe Bay
Min.
23.1
27.3
24Sep – 21Jan
Max.
29.1
34.7
(n = 121 days)
Mean
25.8
33.4
Table 6.
Results of the pre-deployment check for the HL4 and DS5X for each deployment site. The DO of
the reference solution is based on the mean of three Winkler titrations of the reference tank during the
exposure. Ambient water was used for the reference solution at each deployment site.
Deployment
Site
Reference
Solution
Measurement
Temperature
Reference
Solution DO
(mg/L)
DS5X DO
(mg/L)
HL4 DO
(mg/L)
MTU
Site Water
11.7
o
C
10.193
NA
nd
CBL
Site Water
21.6
o
C
7.983
8.15
8.21
HIMB
Site Water
26.6
o
C
6.547
6.55
6.74